HT HT7051 User manual

Copyright HT ITALIA 2021 Release EN 3.01 - 26/11/2021
ENGLISH
User manual

HT7051 - HT7051N
EN - 1
TABLE OF CONTENTS
1PRECAUTIONS AND SAFETY MEASURES ..................................................................2
1.1Preliminary instructions......................................................................................................... 2
1.2During use............................................................................................................................. 3
1.3After use................................................................................................................................ 3
1.4Definition of measurement (overvoltage) category ............................................................... 3
2GENERAL DESCRIPTION..............................................................................................4
2.1Instrument features ............................................................................................................... 4
3PREPARATION FOR USE..............................................................................................4
3.1Initial inspections................................................................................................................... 4
3.2Power supply ........................................................................................................................ 4
3.3Storage ................................................................................................................................. 4
4NOMENCLATURE ..........................................................................................................5
4.1Instrument description........................................................................................................... 5
4.2Description of function keys .................................................................................................. 5
4.3Description of display............................................................................................................ 6
4.4Description of measuring leads............................................................................................. 7
4.5GUARD lead ......................................................................................................................... 7
4.6Notes on the insulation measurements................................................................................. 7
5OPERATING INSTRUCTIONS........................................................................................8
5.1Switch on the instrument....................................................................................................... 8
5.1.1Auto Power OFF ........................................................................................................................ 8
5.2Insulation measurement in FIX mode ................................................................................... 9
5.2.1Configuration of the test parameters for FIX mode.................................................................. 12
5.3Insulation measurement in ADJUST mode......................................................................... 13
5.3.1Configuration of the test parameters for ADJUST mode ......................................................... 16
5.4Insulation measurement in RAMP mode ............................................................................ 17
5.4.1Configuration of the test parameters for RAMP#1 mode......................................................... 21
5.4.2Configuration of the test parameters for RAMP#2 mode......................................................... 21
5.4.3Configuration of the test parameters for RAMP#3 mode......................................................... 22
5.5Enable/Disable of SMOOTH function ................................................................................. 22
5.6Anomalous situations.......................................................................................................... 22
6MANAGEMENT OF MEMORY DATA ...........................................................................25
6.1Save measurements ........................................................................................................... 25
6.2Delete measurements......................................................................................................... 25
6.3Recall measurements ......................................................................................................... 26
7RESET OF INSTRUMENT ............................................................................................26
8CONNECTION OF THE INSTRUMENT TO PC ............................................................26
9MAINTENANCE ............................................................................................................27
9.1General information ............................................................................................................ 27
9.2Recharging internal battery................................................................................................. 27
9.3Cleaning the instrument ...................................................................................................... 27
9.4End of life ............................................................................................................................ 27
10TECHNICAL SPECIFICATIONS ...................................................................................28
10.1Reference guidelines .......................................................................................................... 29
10.2General characteristics ....................................................................................................... 29
10.3Environment........................................................................................................................ 30
10.3.1Environmental conditions for use............................................................................................. 30
10.4Accessories......................................................................................................................... 30
11SERVICE.......................................................................................................................31
11.1Warranty conditions ............................................................................................................ 31
11.2Service ................................................................................................................................ 31
12THEORETICAL APPENDIX ..........................................................................................32
12.1Polarization Index (PI)......................................................................................................... 32
12.2Dielectric Absorbtion Ratio (DAR)....................................................................................... 32

HT7051 - HT7051N
EN - 2
1 PRECAUTIONS AND SAFETY MEASURES
The instrument has been designed in compliance with standards IEC/EN61557-1 and
IEC/EN61010-1 regarding electronic measuring instruments.
CAUTION
For the operator’s safety and to prevent damaging the instrument, follow the
procedures described in this manual and carefully read all notes preceded by
the symbol .
Before and during measurements, carefully observe the following instructions:
Do not perform any measurement in humid environments, in the presence of gas or
explosive or inflammable material or in dusty areas
Even when no measurements are being performed, avoid any contact with the circuit
being tested, with exposed metal parts, with unused measuring leads or circuits, etc
Do not perform any measurement when anomalies are found in the instrument, such as
deformations, breaks, substance leaks, no display view, etc
Pay special attention when measuring voltages above 25V in special environments
(building yards, swimming pools, etc.) and 50V in ordinary environments, as there is
the danger of electric shocks.
In this manual and on the instrument, the following symbols are used:
CAUTION: it is necessary to consult the instruction manual to find the type of
potential danger and the actions to be taken.
Observe the instructions reported in the manual. An improper use could damage
the instrument and lead to dangerous situations for the operator.
DC voltage or current.
AC voltage or current.
Dangerous voltages: risk of electric shocks.
Instrument with double insulation.
1.1 PRELIMINARY INSTRUCTIONS
This instrument has been designed for use in an environment with pollution level 2
It may also be used to test industrial electrical systems up to overvoltage category IV
600V to earth with maximum voltage 600V between inputs
Follow the usual safety rules to protect the operator from dangerous currents and
protect the instrument against improper use
Never use the instrument resting on the floor, it must be placed over flat horizontal
surfaces
Only the accessories supplied with the instrument guarantee safety standards. They
must be in good conditions and replaced, if necessary, with identical models
Do not measure systems exceeding the current and voltage limit values specified
Do not perform measurements in environmental conditions not within the limit values
indicated in this manual
Before connecting the probes to the circuit to be tested, check that the correct function
is selected.

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1.2 DURING USE
Carefully read the following recommendations and instructions:
CAUTION
Failure to observe the cautions and/or instructions may damage the instrument
and/or its components or generate a danger for the operator. If, during use,
the low battery symbol appears on the display, insert the supply cable into the
Europlug socket to start battery recharge. During battery recharge, it is
possible to perform measurements.
Before selecting a new function, disconnect the measuring probes from the circuit
When the instrument is connected to the circuit being tested, never touch any unused
lead
Avoid measuring resistance with external voltages; even if the instrument is protected,
as an excess voltage may cause instrument malfunctions
Prevent that the instrument receives voltage during measurement (e.g. a probe slipping
from the measuring point and touching a point under voltage)
Avoid inserting the plug of the supply cable into the Europlug socket while measuring.
1.3 AFTER USE
When measurements are completed, turn off the instrument by pressing the ON/OFF key.
1.4 DEFINITION OF MEASUREMENT (OVERVOLTAGE) CATEGORY
Standard "IEC/EN61010-1: Safety requirements for electrical equipment for measurement,
control and laboratory use, Part 1: General requirements", defines what is intended for
measurement category, commonly known as overvoltage category. In § 6.7.4: Measuring
circuits, it reads:
Circuits are divided into the following measurement categories:
Measurement category IV is for measurements performed at the source of a low-
voltage installation
Examples are electric counters and measurements on primary devices protecting
against overcurrents and on ripple adjusting units
Measurement category III is for measurements performed on installations inside
buildings
Examples are measurements performed on distribution boards, circuit breakers, wiring
harnesses, including cables, bars, junction boxes, switches, sockets of fixed
installations and appliances designed for industrial use and other equipment, e.g.
stationary motors connected to fixed systems.
Measurement category II is for measurements performed on circuits directly
connected to the low-voltage installation.
Examples are measurements performed on household appliances, portable tools and
similar equipment.
Measurement category I is for measurements performed on circuits not directly
connected to the MAINS.
Examples are measurements performed on circuits not derived from the MAINS and on
circuits derived from the MAINS provided with a special (internal) protection. In this
latter case, the stress caused by the transients is variable; therefore, (OMISSIS) it is
necessary that the user knows the appliance’s resistance to transients.

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2 GENERAL DESCRIPTION
The instrument You purchased, if used in compliance with the indications given in this
manual, guarantees accurate and reliable measurements and the utmost safety thanks to
a development of new conception which ensures double insulation and, consequently,
compliance with the requirements of overvoltage category IV.
2.1 INSTRUMENT FEATURES
Insulation resistance measurement with nominal voltage which can be set up to 5kV
Dielectric leakage current measurement
Polarization Index (PI) measurement
Dielectric Absorption Ratio (DAR) measurement
Capacitance measurement.
AC/DC voltage measurement up to 600V
3 PREPARATION FOR USE
3.1 INITIAL INSPECTIONS
Before shipment, the instrument’s electronics and mechanics have been inspected. All
possible precautions have been taken in order for the instrument to be delivered without
damage. However, we recommend generally inspecting the instrument in order to detect
any damage suffered during transport. Should you detect any anomalies, immediately
contact the forwarding agent or the dealer. Moreover, we recommend checking that the
package contains all parts listed in § 10.4. Should you find any discrepancy, please
contact the dealer. Should it become necessary to return the instrument, please follow the
instructions reported in § 11.
3.2 POWER SUPPLY
The instrument is power-supplied through internal batteries which are recharged from the
mains by means of a battery charger integrated in the instrument itself. The symbol
“” steadily illuminated in the right bottom part indicates that the batteries are flat and
must be recharged. To recharge the batteries, follow the instructions given in § 9.2.
CAUTION
Perform at least a complete recharging of internal battery in one year. If
the instrument is not used for one year, the battery can be damaged and could
not be completely recharging neither after some charging/discharging cycles.
3.3 STORAGE
In order to guarantee accurate measurements and protect the instrument from possible
failures, after a long storage period under extreme environmental conditions, wait for the
instrument to return to a normal condition (see § 10.3.1).

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4 NOMENCLATURE
4.1 INSTRUMENT DESCRIPTION
CAPTION:
1. Input bushings
2. Europlug socket
3. RS-232 connector
4. FUNC/ERASE MEM key
5. Multifunction arrow keys
6. ESC/RECALL MEM key
7. SET/DISPLAY MEM key
8. SAVE key
9. START/STOP key
10.ON/OFF/ key
11.MODE/CLEAR SMOOTH key
12.LCD display
Fig. 1: Instrument description
4.2 DESCRIPTION OF FUNCTION KEYS
Key Description
Multifunction arrow keys they have several functions which
are described in detail below
ON/OFF/ key used for:
Switch on/off the instrument
Switch on the display’s backlighting for 20 seconds (short
pressing of the key with the instrument already on)
FUNC/ERASE MEM key used for:
Select the desired function
Delete the measurements saved during the display of
memory data
MODE/CLEAR SMOOTH key used for:
Change the internal modes (if there are more available
modes)
The pressure of the key set the default value of the selected
parameter
SET/DISPLAY MEM key used for:
Set the test parameters of a function
The pressure of the key shows the dates of the
measurement saved inside the memory

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ESC/RECALL MEM key used for:
Access to the data saved in the memory (if present)
From a parameter setting screen or memory data display
screen, pressing the key once allows returning to the
previous screen
SAVE key used for:
Once a measurement has been completed, pressing the
key once allows saving the results in the memory
From a parameter setting screen, pressing the key once
allows saving the changes made to the parameters
START/STOP key used for:
Start and/or stop a measurement
Table 1: Description of function keys
4.3 DESCRIPTION OF DISPLAY
Symbol Description
Display group 1 shows:
Insulation resistance
Dielectric leakage current
PI (Polarization Index)
DAR (Dielectric Absorption Ratio)
Capacitance
Display group 2 shows:
Nominal test voltage
Generated test voltage
Display group 3 shows the duration time of the test
Bargraph
Modes available test : FIX, ADJUST and RAMP
, , “Flash”, Alarm (values over limits), “Warning” symbols
, , “Low battery", “Mains supply", “Timer” symbols
“Number of test cycles” symbol
Table 2: Description of symbols of display

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4.4 DESCRIPTION OF MEASURING LEADS
CAPTION:
1. Hand protection
2. Safety areas
Fig. 2: Measuring leads
4.5 GUARD LEAD
In some cases, measurements could be affected by surface currents. By applying voltage
to an insulation to be measured, there may be two distinct currents: one flowing in the test
piece, the other flowing on its surface. In case you want to measure only the resistance
due to current Im flowing in the test piece Rx (which is the significant one), it is necessary
to absorb the surface current If using another lead.
Fig. 3: Currents flowing in the test piece
4.6 NOTES ON THE INSULATION MEASUREMENTS
Measuring a high resistance such as the insulation resistance is very difficult as the value
of the currents considered may be very low. When measuring, to prevent making
mistakes, it is therefore necessary to take the following precautions:
CAUTION
Keep the measuring leads suspended above the path or, anyway, make
sure the leads do not make contact in more of one point
While measuring high resistances, the area around the measuring
instrument and the appliance being tested must be free. It is recommended
to use the timer function so that the operator may keep at due distance
from the leads and from the resistance to be tested
It is recommended to use the GUARD lead to measure resistances of
some tens of Gor higher
While use the instrument with main supply, it's important to check
that the earthed resistance pole to measure is connected to the
instrument Rx+ Terminal

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5 OPERATING INSTRUCTIONS
5.1 SWITCH ON THE INSTRUMENT
After switch on, the instrument gives a short
acoustic signal and, for approximately one
second, all segments of the display appear.
Then, the instrument shows the firmware
version, then it sets to the last measuring
mode selected before turning off.
5.1.1 Auto Power OFF
If no test is being carried out, the instrument automatically turns off after approximately 5
minutes after the last time a key was pressed. To reactivate the instrument, it is necessary
to turn it on again by pressing the relevant key.

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5.2 INSULATION MEASUREMENT IN FIX MODE
This measurement mode, performed in compliance with IEC/ EN61557-2 guideline, allows
a quick selection of the test voltage among the values: 250, 500, 1000, 2500, and
5000VDC.
CAUTION
The instrument may be used on installations of overvoltage category CAT
IV 600V to earth with maximum voltage 600V between inputs. Do not
connect the instrument to installations with voltages exceeding the limit
values indicated in this manual. If these limit values are exceeded, the
operator may be exposed to electrical shocks and the instrument could get
damaged

A
lways connect the measuring leads to the instrument and to the alligator
clips with the accessories disconnected from the system
It is recommended to hold the alligator clip respecting the safety area
marked by the hand protection (see § 4.4)
Fig. 4: Instrument connection
1. Turn on the instrument by press ON/OFF/ key
2. Press the FUNC/ERASE MEM key to select the “FIX” mode
3. The display shows a screen similar to
that reported here to the side, which
contains:
The FIX selected mode
The bargraph set to zero
The "--- TΩ" indication
The selected test voltage
The test time value
The plug symbol (if the instrument
is supplied from the mains)
The battery symbol steadily
illuminated or flashing (if batteries
are flat or are being recharged)
The TIMER symbol if the duration
of the test has been set

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4. By pressing the arrow keys, the
instrument shows a screen similar to
that reported here to the side, which
contains the value of the input voltage.
5. Press the MODE/CLEAR SMOOTH key to set one of the following test voltages:
250V, 500V, 1000V, 2500V, 5000V
6. Insert the measuring leads into the relevant input leads of the instrument -Rx, +Rx
and GUARD, if necessary (see § 4.5 and Fig. 4)
CAUTION
Make sure that there is no voltage at the ends of the measuring points before
connecting them to the measuring leads.
7. Connect the alligator clips to the part of the system to be tested
8. Press the START/STOP key to perform measurement
CAUTION
The display shows the message "Measuring..." which indicates that the
instrument is performing the measurement. During this whole phase:
Do not disconnect the measuring leads of the instrument from the
conductor being tested; the conductor could remain live at a dangerous
voltage because of possible stray capacitances in the circuit tested;
Never insert the power cord into the Europlug socket.
9. During measurement, the instrument
gives a short acoustic signal every
second and the display shows a
screen similar to that reported here to
the side, which contains:
The FIX selected mode
The bargraph proportional to the
measured resistance value
The numerical indication of the
measured resistance
The applied test voltage
The symbol of the alarm bell (if the measured value is not within the set limits
and/or if the value of the test voltage is lower than the set nominal value)
The value of the test time elapsed or remaining (if a test has been set)
The plug symbol (if the instrument is supplied from the mains)
The battery symbol steadily illuminated or flashing (if batteries are flat or are
being recharged)
The timer symbol if the duration of the test has been preset
The two "flash" symbols to indicate a dangerous voltage
The message "MEASURING..."

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While measuring, it is also possible to display the leakage current, the DAR (Dielectric
Absorption Ratio if test duration > 1 minute), the PI (Polarization Index if test duration > 10
minutes) which cyclically show when pressing the arrow keys (see § 12.1)
10. If no measuring time was set when setting the parameters or if you want to stop the
test in advance before the set time elapses, press the START/STOP key
11a. Once measurement is complete and
any capacitance has been discharged,
the instrument shows:
The value of the measured
insulation resistance;
The value of the generated voltage;
The duration of the test
If the measured resistance value is
between the (MIN - MAX) limits
previously set, the instrument
shows OK and gives a double
acoustic signal (see § 5.4.1)
OR
11b. Once measurement is complete and
any capacitance has been discharged,
the instrument shows:
The value of the measured
insulation resistance
The value of the generated voltage
The duration of the test
If the measured resistance value is
not between the (MIN - MAX) limits
previously set, the instrument
shows NOT OK, the alarm bell and
gives a long acoustic signal (see §
5.4.1)
12. Once measurement is complete, it is also possible to display the leakage current, the
DAR (Dielectric Absorption Ratio), the PI (Polarization Index) and the capacitance
which cyclically show when pressing the arrow keys (see § 12.1)
CAUTION
If the measured resistance value < 5.0M, the screen displaying the
capacitance shows three hyphens “---“, to indicate that it was impossible to
measure the capacitance, and the symbol
If, when scrolling the results obtained, the capacitance value is > 1nF, it is
recommended to repeat the measurement by activating the SMOOTH
function (see § 5.5)
13. Measures can be saved by pressing the SAVE key twice (see § 6.1)

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5.2.1 Configuration of the test parameters for FIX mode
a. By cyclically pressing the SET/DISPLAY MEM key, it is possible to select the
following parameters:
Minimum value of the insulation (MIN) in a range between 0,01M- MAX
Maximum value of the insulation (MAX) in a range between (MIN) - 10T
Test time value in a range between (00min:05sec) - (99min:59 sec)
b. Press the arrow keys to change the value of the parameters (a long pressing of the
keys allows a rapid change of the values)
c. Press the MODE/CLEAR SMOOTH key to remove the limit values set for the
parameters. The display shows the message "no" to indicate that there is no limit set.
d.
After setting, press the SAVE key to save the changes made or press the
ESC/RECALL MEM key to exit without saving and return to the previous screen

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5.3 INSULATION MEASUREMENT IN ADJUST MODE
This function is performed in compliance with IEC/ EN61557-2 guideline. The ADJUST
mode allows the fine adjustment of the test voltage between 100 - 5000VDC.
CAUTION
The instrument may be used on installations of overvoltage category CAT
IV 600V to earth with maximum voltage 600V between inputs. Do not
connect the instrument to installations with voltages exceeding the limit
values indicated in this manual. If these limit values are exceeded, the
operator may be exposed to electrical shocks and the instrument could get
damaged

A
lways connect the measuring leads to the instrument and to the alligator
clips with the accessories disconnected from the system
We recommend holding the alligator clip respecting the safety area marked
by the hand protection (see § 4.4)
Fig. 5: Instrument connection
1. Turn on the instrument by pressing the relevant key
2. Press the FUNC/ERASE MEM key to select the “ADJUST” mode
3. The display shows a screen similar to
that reported here to the side, which
contains:
The ADJUST function selected
The bar graph set to zero
The indication "--- TΩ"
The test voltage
The value of the test time
The plug symbol (if the instrument
is supplied from the mains)
The battery symbol steadily
illuminated or flashing (if batteries
are flat or are being recharged)
The timer symbol if the duration of
the test has been preset

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4. By pressing the arrow keys, the
instrument shows a screen similar to
that reported here to the side, which
contains the value of the input voltage.
5. Make sure that the set test voltage is the desired one. Should it not be the case,
please refer to § 5.3.1 to change it
6. Insert the measuring leads into the relevant input leads of the instrument -Rx, +Rx
and GUARD, if necessary (see § 4.5 and Fig. 5)
CAUTION
Make sure that there is no voltage at the ends of the measuring points before
connecting them to the measuring leads.
7. Connect the alligator clips to the part of the system to be tested.
8. Press the START/STOP key to perform measurement
CAUTION
The display shows the message “Measuring…” which indicates that the
instrument is performing the measurement. During this whole phase:
Do not disconnect the measuring leads of the instrument from the
conductor being tested; the conductor could remain live at a dangerous
voltage because of possible stray capacitances in the circuit tested
Never insert the power cord into the Europlug socket.
9. During measurement, the instrument
gives a short acoustic signal every
second and the display shows a
screen similar to that reported here to
the side, which contains:
The ADJUST function selected
The bar graph proportional to the
measured resistance value
The numerical indication of the
measured resistance
The actual test voltage
The symbol of the alarm bell (if the measured value is not within the set limits
and/or if the value of the test voltage is lower than the set nominal value)
The value of the test time elapsed or remaining (if a test has been set)
The plug symbol (if the instrument is supplied from the mains)
The battery symbol steadily illuminated or flashing (if batteries are flat or are
being recharged)
The timer symbol if the duration of the test has been preset
The two “flash” symbols to indicate a dangerous voltage
The message “MEASURING…”

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While measuring, it is also possible to display the leakage current, the DAR
(Dielectric Absorption Ratio if test duration > 1 minute), the PI (Polarization Index if
test duration > 10 minutes) which cyclically show when pressing the arrow keys (see
§12.1)
10. If no measuring time was set when setting the parameters or if you want to stop the
test in advance before the set time elapses, press the START/STOP key
11a. Once measurement is complete and
any capacitance has been discharged,
the instrument shows:
The value of the measured
insulation resistance
The value of the generated voltage
The duration of the test
If the measured resistance value is
between the (MIN - MAX) limits
previously set, the instrument
shows OK and gives a double
acoustic signal (see § 5.3.1)
OR
11b. Once measurement is complete and
any capacitance has been discharged,
the instrument shows:
The value of the measured
insulation resistance
The value of the generated voltage
The duration of the test
If the measured resistance value is
not between the (MIN - MAX) limits
previously set, the instrument
shows NOT OK, the alarm bell and
gives a long acoustic signal (see §
5.3.1)
12. Once measurement is complete, it is also possible to display the leakage current, the
DAR (Dielectric Absorption Ratio), the PI (Polarization Index) and the capacitance
which cyclically show when pressing the arrow keys (see § 12.1)
CAUTION
If the measured resistance value < 5,0M, the screen displaying the
capacitance shows three hyphens “---“, to indicate that it was impossible to
measure the capacitance, and the symbol
If, when scrolling the results obtained, the capacitance value is > 1nF, it is
recommended to repeat the measurement by activating the SMOOTH
function (see § 5.5)
13. Measures can be saved by pressing the SAVE key twice (see § 6.1)

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5.3.1 Configuration of the test parameters for ADJUST mode
a. By cyclically pressing the SET/DISPLAY MEM key, it is possible to select the
following parameters:
Minimum value of the insulation (MIN) in a range between 0,01M- MAX
Maximum value of the insulation (MAX) in a range between (MIN) - 10T
Value of the test voltage in a range between 100V - 5000V (can be set in steps of
25V up to 1000V and in steps of 50V from 1000V to 5000V)
Test time value in a range between (00min:05sec) - (99min:59 sec).
b. Press the arrow keys to change the value of the parameters (a long pressing of the
keys allows a rapid change of the values).
c. Press the MODE/CLEAR SMOOTH key to remove the limit values set for the
parameters. The display shows the message "no" to indicate that there is no limit set.
Only when setting the value of the test voltage, by pressing the MODE/CLEAR
SMOOTH key, the voltage sets to the default value of 1000V.
d. After setting, press the SAVE key to save the changes made or press the
ESC/RECALL MEM key to exit without saving and return to the previous screen

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5.4 INSULATION MEASUREMENT IN RAMP MODE
This function is performed in compliance with standard IEC/ EN61557-2. The RAMP mode
allows choosing among three different types of ramps:
RAMP#1 RAMP#2 RAMP#3
For each type of ramp, it is possible to set the duration, the test voltage and the number of
times the ramp is repeated (§ 5.4.1, § 5.4.2, § 5.4.3).
RAMP#1: Voltage starts from 0V, reaches the value V1 in a time interval T, keeps the
value V1 for a time T1, and finally returns to 0 (with possible discharge of the
residual voltage).
RAMP#2: Voltage starts from 0V, which is kept for a time T0, reaches the value V1 in a
time interval T, and finally returns to 0 (with possible discharge of the
residual voltage).
RAMP#3: Voltage starts from 0V, which is kept for a time T0, reaches the value V1 in a
time interval T, keeps to value V1 for a time T1, and finally returns to 0 (with
possible discharge of the residual voltage).
CAUTION
The instrument may be used on installations of overvoltage category CAT
IV 600V to earth with maximum voltage 600V between inputs. Do not
connect the instrument to installations with voltages exceeding the limit
values indicated in this manual. If these limit values are exceeded, the
operator may be exposed to electrical shocks and the instrument could get
damaged

A
lways connect the measuring leads to the instrument and to the alligator
clips with the accessories disconnected from the system
It is recommended to hold the alligator clip respecting the safety area
marked by the hand protection (see § 4.4)
Fig. 6: Instrument connection
1. Turn on the instrument by press the ON/OFF/ key
2. Press the FUNC key to select the RAMP function.

HT7051 - HT7051N
EN - 18
3. The display shows a screen similar to
that reported here to the side, which
contains:
The RAMP type selected
The bar graph set to zero
The indication "--- T"
The set test voltage
The value of the test time
The plug symbol (if the instrument is
supplied from the mains)
The battery symbol steadily
illuminated or flashing (if batteries
are flat or are being recharged)
The timer symbol if the duration of
the test has been preset.
4. By pressing the arrow keys, the
instrument shows a screen similar to
that reported here to the side, which
contains the value of the input voltage.
5. Insert the measuring leads into the relevant input leads of the instrument -Rx, +Rx
and GUARD, if necessary (see § 4.5 and Fig. 6)
CAUTION
Make sure that there is no voltage at the ends of the measuring points before
connecting them to the measuring leads.
6. Connect the alligator clips to the part of the system to be tested.
7. Press the START/STOP key to perform measurement.
CAUTION
The display shows the message "Measuring..." which indicates that the
instrument is performing the measurement. During this whole phase:
Do not disconnect the measuring leads of the instrument from the
conductor being tested; the conductor could remain live at a dangerous
voltage because of possible stray capacitances in the circuit tested
Never insert the power cord into the Europlug socket

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EN - 19
8. During measurement, the instrument
gives a short acoustic signal every
second and the display shows a screen
similar to that reported here to the side,
which contains:
The RAMP function selected
The bar graph proportional to the
measured resistance value
The numerical indication of the
measured resistance
The segment relevant to the current ramp point, flashing
The actual test voltage (relevant to the current ramp point)
The symbol of the alarm bell (if the measured value is not within the set limits
and/or if the value of the test voltage is lower than the set nominal value)
The value of the remaining test time (relevant to the current ramp point)
The plug symbol (if the instrument is supplied from the mains)
The battery symbol steadily illuminated or flashing (if batteries are flat or are
being recharged)
The timer symbol
The two "flash" symbols to indicate a dangerous voltage
The message "MEASURING..."
While measuring, it is also possible to display the leakage current, the capacitance
the number N of the cycle the instrument is performing, which cyclically show when
pressing the arrow keys.
9. If you want to stop the test in advance before the set number N of cycles is reached,
press the START/STOP key.
10a. Once measurement is complete and
any capacitance has been discharged,
the instrument shows:
The value of the measured
insulation resistance
The value of the actually generated
voltage V1
The value of the time relevant to
parameter T1
If the measured resistance value is
between the (MIN - MAX) limits
previously set, the instrument shows
OK and gives a double acoustic
signal (see § 5.4.1, § 5.4.2, § 5.4.3)
OR